Hello all.

I need your help, please. I own a 1979 CJ7 5.0 Ltr V8 auto, and it currently has some General Grabber AT 32x11.5 R15´s.

However I live in Europe, where all the tire sizes are in metric.

I ordered some Bridgestone Dueler 673 tyres, 215x 75/R15, but I am concerned that they arent the same size as the previous ones.

Ideally I want to keep the same ground clearence, but having looked on the web for a couple of hours I have drawn a blank.

I just ordered the Bridgestones, but reading your article on tyre sizes and ground clearance it gives I am worried I will drop a clanger and order the wrong tires, but if I can find out the same size in metric as I had before maybe i can change the order before its too l8.

Dam, wish i read your article b4 i ordered them

thanks all.

Wow i hope that was a typo and you meant 315-75-15.  I used to run a bronco with 32-11.50-15s and I really liked them.  MY eveyday driver is a 99 s-10 blazer.  I run 235-75-15s on them and they're about 28" tall.   I was wondering about putting the 32s on my blazer at one point and measured to find the 4 inch differnce.  If you got 215s then you're going to be running pretty small.

Your 215/75R15's would be about 27.7" tall.  A 285/75R15 would be almost 32" tall and 11" wide.

This is a little bit confusing but I tried to give you a conversion formula for metric to standard measurements.  Hope this explains it well enough for you.

The metric conversion for your tire size is as follows:

215 x 75% x 2 / 25.4 = 12.7  and then   12.7 + 15 = 27.7 inches tall

The basic formula for any tire size reads something like this:

W x S x 2 / 25.4 = I   and add I + R= Tire height in inches.

W is tread width (215 in your case)

S is sidewall height as a percentage of tread width (75% in your case)

2 is because the total tire height has two sidewalls in it (6.35" each)

25.4 millimeters in an inch

I is your total height of the sidewalls(12.7")

R is the diameter of your rim(15")

man i really hope you read that somewhere and if not I hope you work for a tire company cause that was some crazy math and knowledge.  Its nice though to see how you can convert those damn metric sizes over to english.  But the point still remains, if you're running 215-75-15s you're going to come up well short of your 32s and quite a bit narrorwer as well.  My gf has a stock geo/chevy tracker and she has the 215s on it that came with the car.  They're a little shorter and thinner than my 235s.  My advice would be to see if you could ship the tires back and exchange them for a bigger size.  And if I'm not mistaken i think bridgestone carries a 32x11.50x15 in the dueler at.

I got bored one night and figured all that crap out from a tire booklet.  Its one of the curses of having an active mind and a dead end job!  It works for any metric tire as long as you put the numbers in the right place. 

Maybe somebody will ask for my tire tread surface area formula sometime?  LOL 

For those of us who are mathematically challenged try this instead;

http://www.4lo.com/4LoCalc.htm

It can do calcs for speedo conversions, axle ratios, etc... and Metric to Imperial tire size conversions.

they're too small.